Engine systems on vehicles, such as hybrid electric vehicles (HEV) and vehicles configured for idle-stop operations, may be configured with a laser ignition system. In addition to initiating cylinder combustion, the laser ignition system may be used during engine starting to accurately determine the position of a piston in each cylinder, enabling an appropriate cylinder to be selected for a first combustion event. As such, this improves the engine's ability to restart.
Laser ignition systems may be periodically diagnosed. In one example, a service technician may remove the laser device to test the system. However, the inventors herein have recognized that potential injuries may occur during such diagnostics. As an example, the laser pulse output by the device during the diagnostics can pose a serious eye safety hazard. For example, if an inexperienced mechanic, unfamiliar with the high peak-power of the laser device, probes or tampers with the laser ignition device during the testing, the laser output can strike someone in the eye, potentially causing irreparable damage.
In one example, some of the above issues may be addressed by a laser ignition safety interlock system and method. The method may comprise adjusting operation of an engine laser ignition device based on a position of the device with respect to an engine cylinder. In this way, the laser device of an engine ignition system can be disabled when taken out of the cylinder.
For example, a laser ignition system may be used to emit high power laser pulses to ignite a cylinder air-fuel mixture during combusting conditions. During non-combusting conditions, the laser ignition system may be used to determine cylinder piston position by emitting low power laser into the cylinder to determine a distance of a piston with respect to the laser ignition device. For example, the distance may be inferred based on a time elapsed since the laser pulse is emitted and the laser pulse is detected. In addition to using the piston position information to select an engine cylinder for an engine restart procedure, the estimated distance may also be used to determine if the laser ignition device has been removed from the cylinder. Specifically, if the inferred distance between the piston and the laser ignition device is greater than a threshold (wherein the threshold is based on the cylinder length or the maximum distance possible between the piston and the device, such as when the piston is at BDC), it may be concluded that the laser device has been removed from the cylinder (e.g., for testing). Accordingly, the laser ignition device is disabled such that no laser pulse is emitted from the device even when requested. The laser ignition device may be re-enabled only upon confirmation that the laser ignition device has been re-installed into the cylinder (such as following a reset input from the operator). In this way, a safety interlock is provided for the laser ignition device which reduces the potential for injuries incurred when the laser device is handled outside of a cylinder.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.